microsoft / microsoft/TypeScript

Readonly indexer and constructor usage: question

Open
#6,781 13 comments 1 reaction 0 assignees View on GitHub

Nobody has claimed this yet.

Awaiting More Feedback Suggestion
Dominant language
Go
Stars
111k
Forks
14.3k
Avg merge
2d 4h
Merged PRs (30d)
132

Description

class A {
    readonly x;
    readonly [x: string]: string;

    constructor() {
        this.x = 5;  // that's okay
        this["a"] = "s"; // that yields an error
    }
}

Is that by design that readonly indexers for the same type in constructor yield errors?

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start with the TypeScript reproduction in the issue and compare the accepted direct property assignment with the rejected indexed assignment inside the constructor. Review the issue's comment discussion to determine the intended readonly-indexer behavior; done means reaching and documenting a settled behavior or implementation direction, since no source file or test is named.

Written by the indexing model from the issue text.

Assessment

Tech stack
typescript
Domain
compilers
Issue type
Bug
Difficulty
5/5
Estimated time
Over a week
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
25/100

Get new issues in your inbox

A short digest of beginner-friendly GitHub issues.